Maximum Number of Events That Can Be Attended [LeetCode 1353]

MaxEvents.py

# Reference : https://www.youtube.com/watch?v=EKZhEN9P2-I

import heapq

class Solution:
    
    def maxEvents(self, events: List[List[int]]) -> int:
        
        # Sort the events in ascending order of their start time
        events.sort(key = lambda x: x[0])
        
        # Get max day till the last event is open
        max_day = max([event[1] for event in events])
        
        # Init
        day = 1
        num_events = len(events)
        event_idx = 0
        event_queue = []
        heapq.heapify(event_queue)
        event_attended = 0
        
        while day <= max_day:
            
            # Add events which can be attended starting from this day
            while event_idx < num_events and events[event_idx][0] <= day:
                heapq.heappush(event_queue, events[event_idx][1])
                event_idx += 1
                
            # Remove all expried events from the queue
            while event_queue and event_queue[0] < day:
                heapq.heappop(event_queue)
            
            # pop event if exist 
            if event_queue:
                heapq.heappop(event_queue)
                event_attended += 1
            
            # Increment no. of days
            day = day + 1
        
        return event_attended